Downhole tool shock absorber with electromagnetic damping

ABSTRACT

A technique facilitates absorption of shock experienced by a tool in a borehole. The technique comprises coupling a tool into a tool string sized for delivery into the borehole. A shock absorber is positioned along the tool string to absorb shock loads incurred by the tool. The shock load experienced by the tool induces an electromagnetic force in the shock absorber which acts in a direction to mitigate the shock load.

CROSS-REFERENCE TO RELATED APPLICATION

The present document is based on and claims priority to U.S. Provisional Application Ser. No. 61/882,992, filed Sep. 26, 2013, which is incorporated herein by reference.

BACKGROUND

Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore is drilled, various forms of well completion components may be installed to control and enhance the efficiency of producing the various fluids from the reservoir. During drilling, production, and/or other phases of operation, downhole tools may be subjected to mechanical impact and/or perforation induced shock loads which can be detrimental to the integrity and functionality of the tool string and tools/instruments carried by the tool string. Shock absorbers have been employed in tool strings, but existing shock absorbers are based on mechanical or hydraulic systems. For example, downhole shock absorbing systems may be made of crushable elements, e.g honeycomb structures, crushable noses, or crushable coils, which offer one-time shock absorption. Springs also have been used as shock absorption elements, but springs are not able to dissipate energy and may provide undesirable bouncing/recoil upon external excitation.

SUMMARY

In general, the present disclosure provides a system and method for absorbing shock in a borehole. The technique comprises coupling a tool into a tool string sized for delivery into the borehole. A shock absorber is positioned along the tool string to absorb shock loads incurred by the tool. The shock load experienced by the tool induces an electromagnetic force in the shock absorber which acts in a direction to mitigate the shock load.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

FIG. 1 is a schematic illustration of an example of a tool string deployed in a borehole and having a tool subject to shock loads, the tool working in cooperation with a shock absorber employing electromagnetic damping, according to an embodiment of the disclosure;

FIG. 2 is a schematic illustration of an example of a shock absorber for use in absorbing shocks along a tool string, according to an embodiment of the disclosure;

FIG. 3 is a schematic illustration of another example of a shock absorber for use in absorbing shocks along a tool string, according to an embodiment of the disclosure;

FIG. 4 is a schematic illustration of another example of a shock absorber for use in absorbing shocks along a tool string, according to an embodiment of the disclosure; and

FIG. 5 is a schematic illustration of another example of a shock absorber for use in absorbing shocks along a tool string, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of some illustrative embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

The disclosure herein generally relates to a system and methodology for absorbing shock in a borehole. For example, a variety of tools may be used in many well related operations or other borehole related operations and those tools can be subjected to shock forces or loads in a variety of situations. For example, undesirable shock loading may occur through mechanical impact, downhole perforation activities, and/or other activities which subject the tools to high force loads. The shock loading may occur in drilling operations, completion operations, production operations, well servicing operations, and/or a variety of other well related operations.

Generally, a tool is coupled into a tool string which is sized for delivery into the borehole. The tool is moved downhole via the tool string and operated downhole to perform a desired function. A shock absorber is positioned along the tool string to absorb shock loads incurred by the tool. The shock load experienced by the tool induces an electromagnetic force in the shock absorber which acts in a direction to mitigate the shock load.

In embodiments described herein, shock absorption is performed via a shock absorption technology based on the use of electromagnetic damping to reduce the effects of shock forces. With electromagnetic damping, an electromagnetic force is induced in the shock absorber due to a relative motion between a conductor and a nearby magnetic field. The induced force is oriented in a direction opposed to the relative motion and, at least in some cases, is nearly proportional to the motion velocity. As a result, abrupt velocity changes are suppressed and the shock load is mitigated, e.g. damped. The shock absorber effectively converts kinetic energy to electrical energy, and this electrical energy can be dissipated via electrical heating so as to avoid undesirable bouncing or recoil. In some embodiments, the shock absorber has a first component and a second component which induce the electromagnetic force when moved relative to each other and the first component and second component can operate without physical contact. This approach provides a robust and low maintenance shock absorbing system.

According to an embodiment, the shock absorber comprises an electromagnetic damper which handles repetitive and/or reciprocating shock loads because the electromagnetic force is able to continuously act against the direction of relative movement between shock absorber components. The embodiment also is able to convert kinetic energy to electrical energy which can be dissipated to electrical heating or otherwise used or stored, e.g. stored in a battery. In some applications, high-temperature magnets and conductors may be used in the shock absorber to ensure reliable performance at high, downhole temperatures. In some embodiments, the relative movement which creates the electromagnetic force may be accomplished between components which remain physically separate, i.e. limited or no physical contact occurs between the moving components.

Embodiments described herein also provide flexibility for use in various applications and environments because the energy absorption capacity can be modeled and optimized. For example, the energy absorption capacity can be modeled and optimized by manipulating system parameters such as coil density, magnetic strength, resistance load in a circuit, geometric dimensions, and/or other system parameters.

Referring generally to FIG. 1, an example of a shock load absorbing system 20 is illustrated. In this embodiment, a tool string 22 is deployed in a borehole 24 and has a tool 26, e.g. a well tool, which may be subjected to shock loads. The tool 26 may comprise a drill bit, a bottom hole assembly component, a completion component, a landing component, and/or a variety of other components which may be utilized in a borehole and subjected to unwanted forces due to shock loads. The tool 26 works in cooperation with a shock absorber 28, and shock absorber 28 employs electromagnetic damping to dissipate the unwanted shock loads. The shock absorber 28 may be coupled directly with tool 26 or mounted at another location along the tool string 22 such that shock loads incurred by tool 26 can be transmitted to the shock absorber 28.

Referring generally to FIG. 2, an example of shock absorber 28 is illustrated. In this example, shock absorber 28 comprises a first component 30 and a second component 32 which are able to move relative to each other to induce an electromagnetic force, as discussed in greater detail below. In the embodiment illustrated, the first component 30 comprises an electromagnetic coil 34 and the second component 32 comprises a permanent magnet 36, such as a stack of permanent magnets 36. The permanent magnet(s) 36 is positioned for relative movement with respect to the electromagnetic coil 34 when shocks are incurred by the well tool 26. In other words, movement of tool 26 is transmitted to one of the components 30, 32 to create the relative movement with respect to the other of the components 30, 32. The relative movement induces an eddy current in the electromagnetic coil 34 which generates a magnetic field resisting the relative movement between first component 30 and second component 32. The resistance to the relative movement has sufficient force to absorb the shock forces, while the electrical energy generated is dissipated to avoid detrimental recoil or bounce.

In the embodiment of FIG. 2, the first component 30 is in the form of an outer sleeve 38 containing the electromagnetic coil 34 and the second component 32 is in the form of an inner rod 40 containing a stack of the permanent magnets 36. The inner rod 40 is slidably received within outer sleeve 38. In some embodiments, the inner rod 40 is received within outer sleeve 38 without physically contacting the outer sleeve 38 and, in such a configuration, the components of shock absorber 28 may be coupled together and supported by other mechanisms. Other embodiments of the shock absorber 28 also may be constructed in a manner such that the first component 30 and the second component 32 remain out of physical contact during relative movement between the first and second components 30, 32.

When there is relative motion between inner rod 40 and surrounding sleeve 38 due to external excitation, e.g. a shock load incurred by tool 26, eddy current is induced in the electromagnetic coil 34. The induced eddy current then generates a magnetic field which opposes the relative motion between the inner rod 40 and the outer sleeve 38 to effectively slow down the movement. During this process, kinetic energy is converted to electrical energy which is dissipated, e.g. dissipated through electrical heating. In some embodiments, an external resistor 42 may be placed in a circuit 44 of electromagnetic coil 34. The external resistor 42 may be selected to adjust or set a rate of energy dissipation.

Depending on the application, a spring 46 may be attached between first component 30 and second component 32 to help buffer the shock load, i.e. to store part of the kinetic energy in case the electromagnetic coil 34 is unable to dissipate the energy quickly enough. The spring 46 can be used to reduce the overall length of the shock absorber 28 by helping buffer the shock load. Spring 46 also may be used to bias the permanent magnet 36 back toward a predetermined position relative to the electromagnetic coil 34. In the example illustrated, spring 46 is positioned within outer sleeve 38 between outer sleeve 38 and inner rod 40. In this manner, spring 46 is able to help buffer the shock load while also serving to bias the inner rod 40 and the outer sleeve 38 back toward a desired relative position. In other words, the spring 46 may be used to reset the position of inner rod 40 within outer sleeve 38 following activation. The resetting ensures that shock absorber 28 is ready for the next shock absorption with consistent performance.

In some applications, a magnetic cushion 48 may be used to complement spring 46 and to provide more buffering of the shock load via magnetic cushioning. However, the magnetic cushion 48 also may be used in lieu of spring 46. By way of example, the magnetic cushion 48 may comprise a pair of permanent magnets 50 arranged with opposing poles to provide a kinetic cushioning during relative movement of first component 30 and second component 32, e.g. during movement of inner rod 40 farther into outer sleeve 38. The magnetic cushion 48 effectively works in parallel with the electromagnetic coil 34 and the permanent magnet 36.

Referring generally to FIG. 3, another embodiment of shock absorber 28 is illustrated. In this embodiment, the first component 30 comprises outer sleeve 38 containing at least one and often a stack of the permanent magnets 36 and the second component 32 comprises inner rod 40 containing the electromagnetic coil 34. Similar to the previously described embodiment, the inner rod 40 is slidably received within outer sleeve 38 and, in some cases, may interact with outer sleeve 38 without physically contacting the outer sleeve 38.

When there is relative motion between inner rod 40 and surrounding sleeve 38 due to external excitation, e.g. a shock load incurred by tool 26, eddy current is induced in the electromagnetic coil 34 of inner rod 40. The induced eddy current again generates a magnetic field which opposes the relative motion between the inner rod 40 and the outer sleeve 38 to effectively slow down the movement. During this process, kinetic energy is converted to electrical energy which is dissipated, e.g. dissipated through electrical heating. Depending on the application, a spring 46 and/or magnetic cushion 48 may be used in combination with the inner rod 40 and outer sleeve 38 to help buffer the shock load and to reset the relative positions of the electromagnetic coil 34 and permanent magnets 36. The external resistor 42 also may be employed in a manner similar to that described above with reference to the embodiment illustrated in FIG. 2.

Referring generally to FIG. 4, another embodiment of shock absorber 28 is illustrated. In this embodiment, the first component 30 and the second component 32 are constructed such that the electromagnetic coil 34 and the permanent magnet 36 are not positioned coaxially. By way of example, the first component 30 and the second component 32 may be constructed so that the electromagnetic coil 34 and the permanent magnet 36 move relative to each other along a parallel plane.

As with the embodiments of FIGS. 2 and 3, relative motion between first component 30 and second component 32 due to external excitation, e.g. a shock load incurred by tool 26, induces an eddy current in the electromagnetic coil 34. The induced eddy current again generates a magnetic field which opposes the relative motion between the first component 30 and the second component 32 to effectively slow down the movement. During this process, kinetic energy is converted to electrical energy which is dissipated through electrical heating or through other techniques. The spring 46 and/or magnetic cushion 48 may be positioned between the first component 30 and the second component 32 to help buffer the shock load and to reset the relative positions of the electromagnetic coil 34 and permanent magnets 36. The external resistor 42 also may be employed in a manner similar to that described above with reference to the embodiment illustrated in FIG. 2.

Referring generally to FIG. 5, another embodiment of shock absorber 28 is illustrated. In this embodiment, the first component 30 comprises outer sleeve 38 which may be formed out of a suitable metal material. The second component 32 comprises inner rod 40 which is formed with a pair of rod portions 52 coupled to a piston 54 slidably mounted within outer sleeve 38. The electromagnetic coil 34 may be positioned along piston 54 as illustrated. The rod portions 52 also may be supported by bearing structures 56 which are sealed to both rod portions 52 and to outer sleeve 38 via appropriate seals 58. The bearing structures 56 enclose piston 54 and create a cavity 60 which may be filled with magneto-rheological fluid 62.

When there is relative motion between inner rod 40 and surrounding sleeve 38 due to external excitation, e.g. a shock load incurred by tool 26, the relative motion induces a magnetic field in the coil 34. The magnetic field aligns the micro-particles of the magneto rheological fluid 62 and thus increases the viscosity of fluid 62. The increased viscosity acts against the relative movement, thus creating a force acting in a direction which mitigates the shock load.

The various components of shock absorber 28 may be formed from a variety of materials and in a variety of configurations. In some applications, for example, the inner rod 40 may be made of iron or with iron elements instead of magnets. Additionally, the electromagnetic coil density, magneto-rheological fluid, magnetic strength, resistance load in the circuit 44, geometric dimensions of the components, and other system configurations and system parameters may be selected or changed to adjust the shock absorber 28 so as to accomplish a targeted performance.

Although a few embodiments of the system and methodology have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. 

What is claimed is:
 1. A system for absorbing shock, comprising: a tool string deployed in a wellbore, the tool string comprising a well tool and a shock absorber positioned to absorb shock loads incurred by the well tool, the shock absorber comprising: an electromagnetic coil; a permanent magnet positioned for relative movement with respect to the electromagnetic coil when shocks are incurred by the well tool and translated to the shock absorber, the relative movement inducing an eddy current in the electromagnetic coil which generates a magnetic field resisting the relative movement with sufficient force to absorb the shock loads acting on the well tool.
 2. The system as recited in claim 1, wherein the electromagnetic coil is part of an outer sleeve.
 3. The system as recited in claim 2, wherein the permanent magnet is positioned on an inner rod received within the outer sleeve.
 4. The system as recited in claim 1, wherein the electromagnetic coil is received within a sleeve comprising the permanent magnet.
 5. The system as recited in claim 1, wherein the permanent magnet comprises a stack of permanent magnets.
 6. The system as recited in claim 1, wherein the shock absorber further comprises a resistor coupled to the electromagnetic coil to provide a control with respect to the rate of energy dissipation.
 7. The system as recited in claim 1, wherein the relative movement creates electrical energy which is dissipated via heating.
 8. The system as recited in claim 1, wherein the shock absorber further comprises a spring to bias the permanent magnet toward a predetermined position relative to the electromagnetic coil.
 9. The system as recited in claim 1, wherein the shock absorber further comprises a magnetic cushion working in parallel with the electromagnetic coil and the permanent magnet.
 10. A method for absorbing shock in a borehole, comprising: coupling a tool into a tool string sized for delivery into the borehole; positioning a shock absorber along the tool string to absorb a shock load acting on the tool; and using a magnetic field to create a force in the shock absorber, the force acting in a direction which mitigates the shock load.
 11. The method as recited in claim 10, further comprising forming the shock absorber with an electromagnetic coil and a permanent magnet positioned for relative movement with respect to the electromagnetic coil when the shock absorber is subjected to the shock load.
 12. The method as recited in claim 11, further comprising locating the electromagnetic coil on a sleeve.
 13. The method as recited in claim 12, further comprising locating the permanent magnet on an inner rod received within the sleeve.
 14. The method as recited in claim 10, wherein using comprises mitigating the shock load by converting kinetic energy to electrical energy which is dissipated through heating.
 15. The method as recited in claim 11, further comprising coupling a resistor to the electromagnetic coil to establish a desired rate of energy dissipation.
 16. The method as recited in claim 10, further comprising moving the tool string downhole into a borehole.
 17. The method as recited in claim 10 further comprising employing magneto-rheological fluid to establish the force via increased viscosity of the magneto-rheological fluid when exposed to the magnetic field.
 18. A system for absorbing shock, comprising: a shock absorber which may be coupled into a tool string, the shock absorber having a first component with an electromagnetic coil and a second component with a permanent magnet, the first component and the second component being mounted in the shock absorber for relative movement with respect to each other under a sufficient shock load, the electromagnetic coil and the permanent magnet acting, when subjected to the relative movement, to create a counterforce which slows the relative movement.
 19. The system as recited in claim 18, wherein the first component comprises a sleeve and the second component comprises a rod.
 20. The system as recited in claim 18, further comprising a well tool, wherein the shock absorber works in cooperation with the well tool to dissipate shock loads incurred by the well tool. 